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Q: Flow straighteners for MAF, improved MAF Tune?

 
Old 05-17-2019, 07:09 AM
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Default Q: Flow straighteners for MAF, improved MAF Tune?

Hello all,

I am continuing the tuning process on my 2008 LS3 Corvette, the car has an ECS1500 supercharger installed. My plan is to run like the factory (both MAF and MAP) while going full MAF at 3000rpm. So far I have gotten the SD tune to a point where I like it, the car runs very smooth and the fuel trims are at a point I can live with. Issues start to unfold when I bring the MAF into the equation, the system just becomes very erratic and difficult to tune especially when I'm running below 2000 rpm. The car has a stock cam so the flow shouldn't be too messy around idle.

The biggest issue is that the frequency from the MAF is all over the place and is thus causing the fueling to also be very erratic. I looked back at some stock idle data that I had and clearly there is a huge difference in airflow "smoothness" after the ECS air system was installed. I have attached three files, the idle airflow trace when the system was stock, idle air flow with ECS, and driving down the road with ECS.

Stock Idle:


ECS Idle:


ECS Driving:


Clearly the flow is MUCH rougher, and it is no wonder that the MAF tune has been a nightmare. I went online and ordered a sheet of 1/2" thick aluminum honeycomb that I plan to stuff down the intake tube just before the MAF, I assume this will help a little bit.


What has been your experience with this? Is there a filtering coefficient in HPTuners that I can apply to the MAF signal? I looked and couldn't seem to find anything. Perhaps there is a way to push more bias on the VE table at lower speeds? I would love to hear what you guys have done.






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Old 05-17-2019, 07:49 AM
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Yes they do help all the jumpy maf signals. I use one in my custom 4" cai for my tbss with a ls3 maf.
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Old 05-17-2019, 08:12 AM
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How thick was the honeycomb you used?
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Old 05-17-2019, 08:14 AM
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Saxon honeycomb airflow straighteners are great.
https://ls1tech.com/forums/pcm-diagn...er-setups.html
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Old 05-17-2019, 08:33 AM
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Damn I really should have ordered from them, I'm going to have to find a way to cut my 12"x12" sheet down to something that will fit. That would have been easier. I hope this helps as its basically unusable as it is now.
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Old 05-17-2019, 09:37 AM
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You have a mechanical problem (flow is actually variable at the sensing wire location), so there is not a filter in HPT that one could apply to fix it. As suspected, your best bet is to physically smooth out the flow at the MAF element. If you have sharp bends or a change in diameter to the pipe prior to the MAF element, you will get changes in raw MAF sensor frequency that the ECU cannot handle. (I had the same issue trying to run the 103mm MAF housing on my turbo LS3) Luckily, a single 3" or 3.5" pipe with the LS3 MAF sensor in it should have enough measurement range for your combo, so there's no need for a change to a giant 4" tube that can have a noisy signal. Make sure the sensor is after a relatively straight section of pipe (to avoid bends that induce turbulence) and when all else fails use the honeycomb (laminar flow element) to smooth the flow enough to get a cleaner reading. If you can't get a smooth raw Hz output, you won't be able to calibrate the MAF curve.
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Old 05-17-2019, 09:45 AM
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Unfortunately, being the card style MAF its not super easy to move. I don't really understand why ECS has it so close to the bend. I'm sure placing it close to the throttle would cause its own issues, but I would imagine it could have been more towards the middle.


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Old 05-17-2019, 09:48 AM
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I'm sure it runs a lot better on the LS2 setup because of how much further back the MAF is placed.

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Old 05-17-2019, 11:12 AM
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not to highjack the thread, but something I've always wondered about. IIRC, on some of the GM 3.8's and the Northstar engines the MAF was in the throttle body or bolted directly to it. I always that would cause a signal issue but if the OEM's do it I guess it works.
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Old 05-17-2019, 11:31 AM
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Originally Posted by LilJayV10 View Post
not to highjack the thread, but something I've always wondered about. IIRC, on some of the GM 3.8's and the Northstar engines the MAF was in the throttle body or bolted directly to it. I always that would cause a signal issue but if the OEM's do it I guess it works.
They could have SW filtered it. The severe negative overlap of OEM motors also helps things compared to our cammed/modified stuff.
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Old 05-17-2019, 12:33 PM
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Originally Posted by DFORESI View Post
Unfortunately, being the card style MAF its not super easy to move. I don't really understand why ECS has it so close to the bend. I'm sure placing it close to the throttle would cause its own issues, but I would imagine it could have been more towards the middle.

Yeah, not great physical placement. If you can get an LFE (honeycomb) in there between the bend and sensor element, you'll prboably see a reduction in raw signal noise. Alternatively, you could weld another fitting further back (perhaps on the other side, or on a completely new piece/bend). I have an APS turbo kit on my LS3 and the MAF is in a similar location, just a little closer to the throttle body with not only a bend, but a "Y" from both intercoolers upstream of the MAF. It works fine without an LFE, so a little change here can mean a lot. My pipe is 3.5" constant diameter too, FWIW.
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Old 05-17-2019, 01:28 PM
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Great post OP was just going to make a thread about this, I was on the fence about adding it to my LS3 maf swap and after seeing this I just placed an order for the Saxon piece.
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Old 05-17-2019, 01:39 PM
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Just took a looked at the A&A kit and the sensor is definitely placed significantly further back. Not hammering on ECS or anything but moving the sensor mount location back is probably something that needs to be considered.


And yes Chris I will try to at least close the loop on this thread, when I get the straightener installed I should be able to show the difference in the MAF signal at idle. I just hope it makes a large difference.
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Old 05-17-2019, 01:40 PM
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A&A MAF placement for reference.
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Old 05-17-2019, 01:52 PM
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Yea mine is a saxon honeycomb. I installed it a few inches before the maf sensor. All my jumpy maf freq hz went away. Normally it would bounce around maybe 3-4 cells. With the honeycomb maybe 1-2 at the most. Alot more stable!
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Old 05-17-2019, 02:01 PM
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Originally Posted by brandon6.0 View Post
Yea mine is a saxon honeycomb. I installed it a few inches before the maf sensor. All my jumpy maf freq hz went away. Normally it would bounce around maybe 3-4 cells. With the honeycomb maybe 1-2 at the most. Alot more stable!
Did you do the 4:1 ?
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Old 05-17-2019, 02:02 PM
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I just checked out Saxon's website. For about $18, that is a no-brainer, especially if it alleviates MAF headaches!
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Old 05-17-2019, 02:13 PM
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Originally Posted by G Atsma View Post
I just checked out Saxon's website. For about $18, that is a no-brainer, especially if it alleviates MAF headaches!
Cant beat the price point.
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Old 05-17-2019, 02:50 PM
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We took the Saxon airflow straightener out that was directly in front of the LS3 slot MAF (the honey comb was physically touching the front of the MAF) because I had read elsewhere that the slot MAFs don't benefit from the honeycomb. My 102mm MAF is about half way between the f-body 85mm lid and the 92mm TB,,, I've read that having the MAF too close to the TB can be bad, and you want a length of straight pipe before the MAF... there doesn't seem to be a happy medium?

https://www.ls1gto.com/forums/archiv.../t-721970.html
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Old 05-17-2019, 03:15 PM
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MAF's DO benefit from an airflow straightener, especially when they're larger MAF/tubing diameter. It was a noticeable improvement on my LS7 MAF pre/post saxon straightener. You vette guys have it easy. My LS7 maf was directly before a 90* coupler AND the TB due to where it had to be located.
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